Weight and HbA1c trajectories following initiation of continuous glucose monitoring in adults with type 1 diabetes: a cohort study using group-based multi-trajectory analysis

Background Continuous glucose monitoring (CGM) improves glycaemic management in adults with type 1 diabetes (T1D), but may be associated with weight gain. We assessed changes in body weight and HbA1c after CGM initiation and characterized weight–glycemia trajectories. Methods We retrospectively analysed 4178 adults with T1D initiating CGM from the DPV registry (DPV-CGM; n=2104) and a pooled Belgian cohort (BE-CGM; n=2074). Outcomes over 24 months were evaluated using paired t-tests and group-based multi-trajectory modelling. In DPV, CGM initiators were compared with matched controls without CGM (n = 2104; matched for sex, age, diabetes duration, baseline weight, and HbA1c). Findings After 24 months, mean body weight increased by 1.8 kg [95% CI: 1.5; 2.0] in DPV-CGM and 1.0 kg [0.8; 1.2] in the BE-CGM cohort, while HbA1c decreased by −0.2% [−0.1; −0.2] and −0.1% [−0.03; −0.1], respectively (all p < 0.0001). In DPV-controls, weight increased by 1.2 kg [0.9; 1.5] (p < 0.01) and HbA1c decreased by 0.06% [−0.001; −0.11] (p = 0.05). Three trajectories were identified. The first showed modest weight gain with HbA1c improvement: 147/2104 (7.0%) DPV-CGM vs 99/2104 (4.7%) DPV-controls, and 411/2074 (19.8%) in BE-CGM. The second, largest group, showed stable weight and HbA1c: 1773/2104 (83.2%) DPV-CGM vs 1612/2104 (74.7%) controls in DPV-controls, and 1447/2074 (69.8%) in BE-CGM. The third, an unfavourable trajectory characterized by substantial weight gain (≈8 kg) with stable HbA1c, included 184/2104 (9.9%) DPV-CGM vs 393/2104 (20.5%) DPV-controls, and 216/2074 (10.4%) in BE-CGM (ꭓ 2 p < 0.01). Interpretation CGM initiation was associated with modest weight gain and improved HbA1c. Compared with matched controls, CGM users were less likely to belong to the unfavourable weight gain with stable HbA1c trajectory, which occurred in 9.9% vs 20.5%, respectively. Funding Innovative Medicines Initiative2 Joint Undertaking under grant agreement No. 875534.